Owing to the popularity of mobile and smart devices, the recent widespread adoption of wireless broadband has resulted in a tremendous growth in the volume of mobile data traffic, and has radical changed the system requirements. For instance, while it has become very critical to lower the complexity, elongate the battery life, and support the highly mobility and service continuity of the devices, higher data rate and bandwidth, and lower latency are also more than ever necessary to support modern applications.
In order to meet the needs of future wireless networks in the past years several physical layer techniques have been introduced (e.g., multiple input multiple output (MIMO) techniques, enhanced inter-cell interference coordination (eICIC) and coordinated multi-point designs, etc.), and more recently an increasing interest has risen in operating cellular networks in unlicensed spectrum to cope the scarcity of licensed spectrum in low frequency band with the aim to further improve the rate. In this context, one of the major enhancement for Long Term Evolution (LTE) in 3GPP Release 13 has been to enable its operation in the unlicensed spectrum via Licensed-Assisted Access (LAA), which expands the system bandwidth by utilizing the flexible carrier aggregation (CA) framework introduced by the LTE-Advanced system. Enhanced operation of LTE systems in unlicensed spectrum is also expected in future releases, and to be further carrier in fifth generation (5G) systems. Potential LTE operation in unlicensed spectrum includes but not limited to 1) the LTE operation in the unlicensed spectrum via dual connectivity (DC)—called DC based LAA herein, and 2) the standalone LTE system in the unlicensed spectrum, where LTE-based technology solely operates in unlicensed spectrum without requiring an “anchor” in licensed spectrum—called MulteFire. MulteFire, combining the performance benefits of LTE technology with the simplicity of Wi-Fi-like deployments, is envisioned as a significantly important technology component to meet the ever-increasing wireless traffic.
MulteFire supports the autonomous uplink transmission without grant from anchored eNB—called grantless uplink (GUL). Also, the same work item is also agreed and started in the 3GPP. According to the current agreement that,
Power control: The SUL reuse the legacy procedure without impact. The GUL power is determined by:
            P              PUSCH        ,        c        ,        GUL              ⁡          (      i      )        =      min    ⁢          {                                                                                    P                                      CMAX                    ,                    c                                                  ⁡                                  (                  i                  )                                            ,                                                                                          10                ⁢                                                      log                    10                                    ⁡                                      (                                                                  M                                                  PUSCH                          ,                          c                          ,                          GUL                                                                    ⁡                                              (                        i                        )                                                              )                                                              +                                                P                                                            O                      ⁢                      _                      ⁢                      PUSCH                                        ,                    c                                                  ⁡                                  (                  j                  )                                            +                                                                                                                                α                    c                                    ⁡                                      (                    j                    )                                                  ·                                  PL                  c                                            +                                                Δ                                      TF                    ,                    c                                                  ⁡                                  (                  i                  )                                            +                                                f                                      c                    ,                    GUL                                                  ⁡                                  (                  i                  )                                                                        }      
where MPUSCH,c,GUL is the bandwidth of the grant less PUSCH resource